up to no good
A flying monster? Why wouldn't a wizard cast Fly on the party fighter(s)? What if the Fighter(s) have magic items that give flight?
Yeah, the fighter could have had a little more utility outside combat, but the fact that a terrible DM can include things that can't be overcome without magic in a game where the fighter does not have magic doesn't make the worthless in general.
Well, this thread has gone full 'if the class isn't the best then it is absolutely useless all the time' as is tradition.